The term is used a lot but I’m not finding a definition, a good place would be in the Dorico concepts or Glossary, unless I missed it. It seems to indicate a bunch of musical content within a Flow, so then the definition would be “A Flow is made up of Systems”. I see references to frames in “system formatting”, but the definition of frames says it’s made up of text, graphics and the like, so is a graphics element a system too?
No biggie but just want to get it clear.
“System” is not Dorico-specific terminology. Elaine Gould’s “Behind Bars” doesn’t bother to define it, but does bother to define “System Dividers”, which are the two diagonal lines that are often inserted in the gaps between two systems.
Wikipedia says:
A vertical line drawn to the left of multiple staves creates a system, indicating that the music on all the staves is to be played simultaneously. A bracket is an additional vertical line joining staves to show groupings of instruments that function as a unit, such as the string section of an orchestra. A brace is used to join multiple staves that represent an instrument, such as a piano, organ, harp, or marimba.[3] Sometimes a second bracket is used to show instruments grouped in pairs, such as the first and second oboes or first and second violins in an orchestra.[4] In some cases, a brace is used for this purpose.[3][5]
When more than one system appears on a page, often two parallel diagonal strokes are placed on the left side of the score to separate them.
It’s a single run of bars from one side of the page to the other.
In an orchestral score, you might only get one system to a page. Here’s an example of that, showing lots of instruments but all playing the same seven bars:
In a string quartet score, you might get four systems to a page. Here’s an example of that, showing a string quartet all playing bars 1-6, then all playing bars 7-10, then bars 11-14, then bars 15-20:
And on the first page of the 1st Violin part for that same string quartet, you’ll see 12 staves which correspond to 12 systems:
If it were a typical piano score, you might get 10 or 12 staves on a page but only five or six systems, because the top two staves are played simultaneously, the next two staves are played simultaneously etc.
Ah thanks, now a lot of bits are making more sense, thanks. I have the Gould book on order. Just saw your edit when I posted this - brilliant examples! Really making sense now.
So I have a system break in the middle of a line, can you tell me how I change the formatting of the previous line? In this case I want the previous system to end with a double vertical line at bar end.
Typically I’d select the final barline of the previous system and type Shift-B || Enter (or Shift-B double Enter). You can also do that from the Bars and Barlines section of the right panel, in Write mode.
Should be as simple as inputting a double barline where you want the double barline. If you wanted the very end of a flow to have a double barline, you can do that in Notation Options.
On a side note, it’s useful to hear from users who would appreciate a term being clarified/defined in the manual - there’s a delicate line between “useful” and “overkill”, so it’s good to know of instances that are perceived to be on one side or the other of that line.
Yeah I was working in the days when paper was the only option and later couldn’t spend the $$ on Sib/Finale. Then when I could afford it they were getting so long in the tooth and warty it didn’t seem worth it 
So I’m really a newb to musical engraving, but it’s a beautiful fascinating subject. So for folks like me who don’t have the working conceptual framework for engraving this is really helpful.
The other thing is knowing the standard conventions. I’ve looked at sheet music for but never thought about it. Dan mentioned in another thread that (using this terminology I know now) “systems always extent to the right margin”. That is there are no partial lines. Anyhow I’ll probably find this kind of info in the Gould book, but if anybody knows of a cheat sheet that would be really helpful.
So the system Flags - e.g. System Break and Frame Break - those are both ways of defining a system right? In other words a Frame brake is also a type of System break, is that the right way to think of it?
Yes I suppose you could think of it like that: specifying where you want a new system to start, but also to start in/move to the next frame (which in most cases is the next page). I wouldn’t think of a frame break as a “type of system break” though - they’re both ways of formatting music in a single layout, i.e. there are breaks: system, and frame.
Gould’s book is excellent. There are other guides too, e.g. by Ted Ross and Kurt Stone.
Maybe it is from interest to underline that the word “System” or more exactly “Notensystem” in german is used for “Staff”.
At the moment I am not aware of a specific term in german for what is called system in this thread.
Interesting, maybe that’s the origin of the term then. I was wondering, it seemed like an odd choice in music.
Any special term for the “Grand Staff” (U.S.) or “Great Staff” (U.K.)?
Klaviersystem
See Wikipedia:
Mehrere gleichzeitig erklingende Notensysteme werden so übereinander notiert, dass alle gleichzeitig erklingenden Noten jeweils senkrecht übereinander stehen. Eine solche Gruppe von Notensystemen wird ebenfalls System oder nach der französischen Bezeichnung für die geschweifte Klammer Akkolade genannt. Die einzelnen Fünflinien-Systeme in diesem System heißen dann Zeilen.
Gelegentlich bezeichnet der Begriff Akkolade nicht die Gesamtheit gleichzeitig erklingender Systeme, sondern nur bestimmte, jeweils durch Klammern (Akkoladenklammern) verbundene Instrumentengruppen einer Partitur.
Thank you HeiPet for the Wikipedia link though I am wondering when this term took this meaning.
I can’t find this meaning in older litterature like Chlapik “Die Praxis des Notengraphikers”.
I also can’t remember that Akkolade was used for a whole score system during the time I studied music, but well this was decades ago 
BTW I have the feeling that notation software has quite a strong influence on the specific terms used for notation.
“Partitursystem” is the term I was looking for.
I would say this is one correct term in german for what is called system in Dorico.
Here then three german terms which should be correct:
(Single) staff: Notensystem
Grand staff: Klaviersystem
System: Partitursystem
Daniel uses »system« in another way. Look here: https://www.steinberg.net/forums/viewtopic.php?f=246&t=201768&e=1&view=unread#unread
A system is both: The groups of staves for an instrument/group AND the staves in a new frame. So, its not totally clear, what Dorico means with »system«.
What? That’s exactly the same definition. You appear to have dragged a text item from one system to another. The fact that one system is on one page and another system is on another page is irrelevant; they’re still two systems.
Incidentally, Ted Ross talks about systems as far back as 1970. The terminology definitely predates notation software.
Thanks for including the Dvorak symphony Pianoleo. It’s one of my all time favourites. Even just reading the score brings me out in chills!
No, you’re misunderstanding me. It doesn’t matter, for the purposes of erasing the background behind a text item, whether the other system is in the same or a different frame. The frame is immaterial, it’s the fact that it’s a different system that matters. (Technically in fact you can at the moment erase the background of a previous system, since each system is drawn one after another, but I would not rely on that behaviour, as it could easily change in future versions of the software. The general principle is that each system is drawn independently, and an item in one system will not affect items in another system.)
Leo’s first reply here is an amazingly comprehensive answer. I am not sure that it all needs to go into the manual, but given that far more basic things are explained in the manual in great detail, some kind of addition would be nice for those who need it. I suggest that such rudiments be collected together in an appendix, because they otherwise clutter sections explaining more Dorico specific aspects. Again, I cannot recall exactly where, but I do remember being exasperated when told to suck eggs at great length during one search! 
David
Tanks, sorry I misunderstood …
Sorry, Daniel! Yes, I misunderstood this. My brain isn’t working properly on mondays …
Today’s Monday? 